Effects of helical distortions on the optical properties of amide NH infrared absorption in short peptides in solution

The relationship between distorted intramolecular H-bonds and infrared absorption properties of the donor NH group in short helical peptides in solution are presented. The helical backbone in the peptides experiences distortions, the extent of which depends on the chain length, that are reflected in both the energy of the stretching mode and the molar extinction coefficient of the intramolecularity H-bonded N-H groups.